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Ss made magnitude estimates of the perceived roughness of grooved aluminum plates. Two aspects of the touching process were altered and their effects upon roughness examined. Roughness increased with increasing finger force, regardless of whether the S or the E chose the values. Rate of hand motion had a negligible effect on perceived roughness, indicating a roughness constancy and providing further evidence of the relative unimportance of vibratory frequency. The effects of these components of the touching process were discussed in terms of an active-passive continuum rather than a dichotomy. Perceived roughness declined with increasing land width (with narrow grooves), although only over the widest half of the land range; there was no land effect when the grooves were wide. In addition to these macrostructural parameters, the effects of two stimulus production techniques were compared. The discrepancies between the two sets of data were interpreted in terms of the microscopic irregularities of the plate surfaces. The findings were briefly related to an analysis of perceived roughness of grooved surfaces in terms of static deformation of the skin.

The availability and salience of object attributes under haptic exploration, with and without vision, were assessed by two tasks in which subjects sorted objects that varied factorially in size, shape, texture, and hardness. In the directed-discrimination task, sub

A set of three experiments was performed to investigate the role of visual imaging in the haptic recognition of raised-line depictions of common objects. Blindfolded, sighted (Experiment 1) observers performed the task very poorly, while several findings converged to indicate that a visual translation process was adopted. These included: (1) strong correlations between imageability ratings (obtained in Experiment 1 and, independently, in Experiment 2) and both recognition speed and accuracy, (2) superior performance with, and greater ease of imaging, twodimensional as opposed to three-dimensional depictions, despite equivalence in rated line complexity, and (3) a significant correlation between the general ability of the observer to image and obtained imageability ratings of the stimulus depictions. That congenitally blind observers performed the same task even more poorly, while their performance did not differ for two-versus three-dimensional depictions (Experiment 3), provides further evidence that visual translation was used by the sighted. Such limited performance is contrasted with the considerable skill with which real common objects are processed and recognized haptically. The reasons for the general difference in the haptic performance of two-versus three-dimensional tasks are considered. Implications for the presentation of spatial information in the form of tangible graphics displays for the blind are also discussed.The haptic perceptual system uses both cutaneous and kinesthetic inputs to derive information about the properties of objects and about their spatial layout (Gibson, 1966;Loomis & Lederman, 1986). Past research has consistently represented haptics as an ineffective system for learning about the concrete world. It has been compared to vision in particularly unfavorable ways. The evidence derives largely from three sets of perceptual tasks: the perception of extent, direction, and position of simple point and line stimuli, the recognition of raised-line drawings of familiar objects, and the recognition of planar nonsense shapes. We will consider each in tum.